Show/hide field and handle security on backend.

Filtered due to lack of support in MySQL < 5.5.3.

After posting a comment to a question the comment anchor is wrong . This
commit fixes this issue with the correct anchor

From PRs by @pupi1985 (unmergeable due to file structure changes).
Closes #69.
Closes #126.

Set to Unix line endings in repo; the gitattributes file means they
will be converted to suit the user’s system.